Stars are opaque. Fortunately, deformations of the stellar surface depend on their interiors [1]}, [2]}, [3]}, [4]}, [5]}, [6]} and as such, asteroseismology is the Rosetta Stone to infer details of stellar structures [5]}, [6]}. Stellar spectra consist principally of low-frequencies gravity (g-) modes and high-frequencies pressure (p-) modes, defining two bands separated by a finite interval of frequencies, also referred as a gap. The stellar spectrum may also be enriched by additional branches, such as surface wave modes confined in the outer regions. In recent years, a novel type of waves propagating in stratified compressible fluids has been discovered. This so-called Lamb-like wave fills the gap between the p- and the g- band. Although this mode bears similarities with the Lamb wave [9]}, [10]}, it is confined around peculiar values specific of the stratification profile, and not at the boundaries. The key point is that these waves have been postulated using arguments from topology [11]}. Modes in the original spatially homogeneous system can be predicted from the analysis of the topological invariant of a simpler dual wave problem with constant coefficients. Similar topological approaches were developed in condensed matter since the eighties, and flourished across all field of physics, including fluid dynamics and plasma over the last few years [12]}, [13]}, [14]}, [15]}.
